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The present thesis deals with the topic of ship manoeuvring in waves and the effects imposed by the shallow water. In this aspect, ship's manoeuvrability is investigated using a numerical method, which was developed according to a hybrid approach where seakeeping and manoeuvring contributions are blended. In order to ensure that the aforementioned model incorporates correctly seakeeping and calm water manoeuvring approaches, separate validation processes are followed beforehand. In case of nonlinear seakeeping analysis, parametric roll investigation is undertaken as well, as a mean to verify that the developed methodology evaluates properly the fundamental external forces, especially roll damping. In this way, a framework is established which offers the ability to perform holistic hydrodynamic assessment of marine vessels as well. Validation of the developed computational code is conducted using experimental turning circle trajectories, which refer to deep water conditions. The case studies concern the horizontal motions of the S-175 container ship at long waves and four values of under keel clearance corresponding to medium-deep (UKC=3.0, 2.5, 2.0) and shallow waters (UKC=1.5). In this aspect, the wave forces as well as the manoeuvring-related ones are corrected using relevant methodologies. In particular, a 3D potential flow method is adopted for the evaluation of the former, whilst corrections are applied on the various manoeuvring-related force components defined by the Manoeuvring Modelling Group (Ogawa et al., 1977). Especially in case of the added resistance, near and far-field methods are implemented based on the size of the wavelength with respect to the ship's length. The empirical corrections which refer to the manoeuvring-related forces and are used in order to incorporate the shallow water effect, concern the hydrodynamic hull forces, the calm water resistance and various hull-rudder-propeller interaction coefficients and are based on regression formulae which are functions of the under keel clearance ratio.